Ethylene terephthalate polymer retaining ring for a chemical mechanical polishing head

ABSTRACT

Embodiments of a retaining ring for use with a chemical mechanical polishing process with a body including a polyethylene terephthalate polymer or polymer including ethylene terephthalate monomers are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority of U.S. provisional application No. 60/839,552, filed on Aug. 22, 2006, the teachings of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to chemical mechanical polishing (CMP), and more particularly, to a retaining ring for use in a CMP apparatus.

2. Description of the State of the Art

The present invention relates to a polishing apparatus for polishing a plate-like article such as a semiconductor wafer or an optical lens. In particular, the invention relates to a retaining ring, an integral part of the polishing apparatus. In manufacturing integrated circuits, optical devices and the like, it is important that a workpiece used to form an integrated circuit, optical device, or the like have a highly planar surface.

A polishing technique referred to as Chemical Mechanical Polishing (CMP) has been commonly employed to polish semiconductor wafers. CMP is a combination of chemical reaction and mechanical buffing. In CMP, a semiconductor wafer held by a rotating carrier body is brought into contact with a polishing surface provided on a rotating turntable while an alkali or acid abrasive slurry is supplied onto the polishing surface, whereby the wafer is polished both mechanically under relative motion between the rotating carrier body and the rotating turntable, and chemically by the supplied slurry. In this way, the wafer surface can be polished to an exceptionally high degree of flatness.

A critical component of a CMP system is a retaining ring. A conventional CMP system includes a polishing head with a retaining ring that holds and rotates the wafer against a pad surface rotating in the opposite direction or same direction. Thus, the function of the retaining ring is to contain and position the wafer as it is being planarized. Also, by adjusting the force on the retaining ring, the removal rate on the edge of the wafer can be adjusted. This is due to a change in the pad rebound characteristics as the force applied to the retaining ring is changed.

With proper material selection and design these rings can offer low wear rates, uniform surface finish with a tight flatness tolerance and absence of large-scale topography in addition to high material stability with low vibration characteristics. An important problem with retaining rings is that they can cause defects on the polished wafer during the polishing process. As the retaining ring and the wafer contact the pad during the polishing process, a particle that is present in the retaining ring material may become dislodged as the retaining ring wears. The dislodged particle can travel on the pad surface under the wafer causing a defect on the wafer. These defects can result in defective die on the wafer, thus decreasing the yield from each wafer.

SUMMARY OF THE INVENTION

Certain embodiments of the present invention include a retaining ring for use in a chemical mechanical polishing process, a body of the retaining ring comprises a PET polymer, wherein the polymer is free or substantially free of inorganic particles.

Further embodiments of the present invention include a retaining ring for use in a chemical mechanical polishing process, a body of the retaining ring comprises a polymer, the polymer comprising ethylene terephthalate monomers, wherein the polymer is free or substantially free of inorganic particles.

Other embodiments of the present invention include a method of polishing a substrate comprising: polishing a substrate with a chemical mechanical polishing apparatus, the apparatus comprising a retaining ring that holds and rotates the substrate against a polishing pad surface, a body of the retaining ring comprising a polymer including a PET polymer, wherein the polymer is free or substantially free of inorganic particles.

Additional embodiments of the present invention include a method of polishing a substrate comprising: polishing a substrate with a chemical mechanical polishing apparatus, the apparatus comprising a retaining ring that holds and rotates the substrate against a polishing pad surface, a body of the retaining ring comprises a polymer, the polymer comprising ethylene terephthalate monomers, wherein the polymer is free or substantially free of inorganic particles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram illustrating a cross section of a prior art retaining ring.

FIGS. 2-3 depict the substrate removal rate as function of position across polished wafers in tests using talc-containing and talc-free retaining rings.

FIGS. 4-7 depict bar charts of defect results on wafers polished using talc-containing and talc-free retaining rings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram illustrating a cross section of a prior art retaining ring, substrate, and pad. A retaining ring 30 is cylindrical in shape and holds a substrate 40 in place during CMP. Retaining ring 30 has an outer portion 10 and a center portion 20. Retaining ring 30 includes a lower surface 32 for contacting a polishing pad 110 during CMP, an inner surface 34 for retaining a substrate, an outer surface 36, a top surface 38, and a topper surface 50 that essentially caps the hollow region of retaining ring 30. Retaining ring 30, in addition to functioning to hold substrate 40 in place, functions to press the pad 110 in a lateral motion during the polishing process. The retaining ring depicted in FIG. 1 is provided as an example only. There are many variations in retaining ring design. The present invention is not limited to the retaining ring design depicted in FIG. 1.

Retaining rings can be made from various kinds of polymers, both filled and unfilled with filler particles. Filler particles or fillers refer to particles dispersed within a polymer. Representative polymers can include, but are not limited to, polyphenylene sulfide (PPS), polyetherketone (PEEK), or polyesters. Fillers can be added to a polymer for a variety of reasons, including, but not limited to, facilitating processing of a polymer or enhancing the mechanical properties of the polymer. A polymer for use in a retaining ring can also include particles that are nucleating agents that are used in the synthesis of the polymer. Representative inorganic fillers include, but are not limited to, talc, alumina, and titanium oxide. It is believed that polymers with inorganic fillers used in retaining rings can increase or cause defects on the polished wafers during polishing.

Various embodiments of the present invention include a retaining ring in which a body of the retaining ring includes or contains a polyethylene terephthalate (PET) polymer that is free or substantially free of inorganic particles. Such inorganic particles may refer to inorganic fillers or inorganic nucleating agents. For example, the PET polymer can be free or substantially free of talc.

Further embodiments of the present invention include a retaining ring in which a body of the retaining ring includes or contains a polymer including ethylene terephthalate (ET) monomer that is free or substantially free of inorganic particles. In an embodiment, the polymer is a copolymer including one or more additional types of monomers or functional groups. For example, additional monomers or functional groups can include, but are not limited to phenylene sulfide and/or etherketone. The copolymer can be a random copolymer or have alternating monomers or functional groups.

In some embodiments, a majority of the copolymer includes ET monomers. In exemplary embodiments, the copolymer can have greater than about 50 wt %, 65 wt %, 80 wt %, 95 wt %, or greater than about 99 wt % ET monomer. In additional embodiments, the present invention can include a retaining ring in which a body of the retaining ring includes or contains a blend of a PET polymer and an ET-containing copolymer. As used herein, “PET/ET” refers to a PET polymer, an ET-containing polymer, and/or a blend of a PET polymer and an ET-containing polymer.

In one embodiment “substantially free” can refer to a weight fraction of inorganic particles in the body or the PET/ET-containing portion of the body of the retaining ring at which substrate defects caused by the inorganic particles during polishing are essentially eliminated or not detectable by standardized measurement techniques. A representative example of a commercially available PET-containing polymer is Ertalyte® PET-P manufactured by Quadrant Engineering Plastic Products of Bridgeport, Conn.

In one embodiment, all or a majority of the body of the retaining ring includes or contains the PET polymer or ET monomers of an ET-containing polymer. Alternatively, a portion of the body of the retaining ring includes or contains the PET or ET-containing polymer. In one embodiment, a portion of the retaining ring that is subjected to wear can include or contain the PET/ET polymer. For example, portion 10 of retaining ring 30 in FIG. 1 can be made from the PET/ET polymer.

In certain embodiments, a majority of the body or the PET/ET-containing portion of the body of the retaining ring can be composed of the PET polymer or ET monomers of the ET-containing copolymer. In some exemplary embodiments, the body or the PET/ET-containing portion of the body of the retaining ring can be greater than about 50 wt %, 65 wt %, 80 wt %, 95 wt %, or greater than about 99 wt % PET or ET monomers of the ET-containing copolymer. In one embodiment, the body or the PET-containing portion of the body of the retaining ring is 100 wt % PET polymer.

In further embodiments, the body or the PET/ET-containing portion of the body of the retaining ring can be a blend of the PET/ET polymer and at least one additional polymer. In one embodiment, the PET/ET polymer and the additional polymer(s) can be a uniform or substantially uniform polymer blend. In an embodiment, the PET/ET polymer and the additional polymer(s) are a miscible blend. Alternatively, the PET/ET polymer and at least one additional polymer are immiscible, so that the PET/ET polymer and the additional polymer form an immiscible blend. The PET/ET polymer and the additional polymer(s) can be mixed or dispersed uniformly or substantially uniformly.

In additional embodiments, the body or the PET/ET-containing portion of the body of the retaining ring can include organic filler particles dispersed within the PET/ET polymer. In some embodiments, the organic particles can decrease the coefficient of friction between the retaining ring and contacting surfaces. It is believed that organic filler particles will not increase the likelihood of defects in a substrate during polishing as is the case with inorganic particles. A representative organic filler is TEFLON. The weight percent of organic filler in the polymer can be less than 0.1%, between 0.1-1%, between 1-2%, or greater than 2%.

In some embodiments, a retaining ring can be fabricated by methods including injection molding or extrusion. In additional embodiments, a polymer can be formed into a stock shape and machined or milled to form a retaining ring using methods that are known in the art.

It has been demonstrated that the use of a PET-based material, Ertalyte® PET-P, without inorganic fillers or inorganic nucleating agents, in a retaining ring results in significantly less defects on the polished wafer while having a similar removal rate and uniformity profiles to commercially available talc-containing Ertalyte®. In addition, the lifetime of a retaining ring made from talc-containing Ertalyte® and retaining rings made from the talc-free material have been shown to be similar. Typically, the lifetime for a retaining ring made from PET material is four times that of PPS and two times that of PEEK, making PET an excellent option as a retaining ring material.

EXAMPLES

The examples and experimental data set forth below are for illustrative purposes only and are in no way meant to limit the invention. The following examples are given to aid in understanding the invention, but it is to be understood that the invention is not limited to the particular materials or procedures of the examples.

A comparison was performed of the break-in time and defects of retaining rings made from Quadrant Ertalyte with talc filler and retaining rings made with talc-free Quadrant Ertalyte.

The experimental setup included a polishing tool, polishing pad, slurry, and wafers. The polishing tool was an F*Rex300 w/300 mm MPTI Multi-Zone Head (Ertalyte SC & DSI) and a 3M A9 Dresser. The polishing pad was an IC1000-P/Suba400 and the slurry was SC-112. The wafers used were thermal Ox (15KÅ) and TEOS (8KÅ). The process conditions were BSP/CZP/SCP/RRP=200/160/120/170 hPa; TT/TR=45/46 rpm. The thickness metrology was a Nanometrics 8300. The defect metrology was a KLA Tencor SP-1.

Removal Rate and Uniformity Comparison

In Table 1 the removal rate (RR) in Angstrom/min and uniformity of wafers using retaining rings made from talc-containing Ertalyte® and talc-free Ertalyte® are compared. As shown, tests were performed for two different wafers. The removal rate and the percent nonuniformity (NU %) are similar for the talc-containing and talc-free retaining rings. 81 pt DS refers to 81 measurement points across the diameter of the wafer and 121 CS refers to 121 measurement points in a polar pattern across the wafer. NU % is a measure of the removal rate variation within the 81 pt DS or 121 pt CS wafers.

FIG. 2 depicts the removal rate as a function of position across the 81 pt DS wafer using the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings. FIG. 3 depicts the removal rate as a function of position or measurement site number across the 121 pt CS wafer using the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings. The removal rate is very similar for both retaining rings.

TABLE 1 Comparison of Removal Rate and Uniformity of retaining rings made from talc-containing Quadrant Ertalyte ® and talc-free Quadrant Ertalyte ®. 81 pt DS 121 pt CS RR (A/min) NU % RR (A/min) NU % Quadrant (Talc) 931 4.59 914 3.65 Quadrant (No Talc) 951 5.25 929 2.71

Run Sequence for Defect and Lifetime Tests

There was a pad break-in of 600 sec for both the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings.

The run sequence for the talc-containing Ertalyte® retaining ring is as follows: 1 Teos Wafer+1 Dummy Ox+1 Teos Wafer+2 Dummy Ox+1 Teos Wafer+3 Dummy Ox+1 Teos Wafer+4 Dummy Ox+1 Teos Wafer+5 Dummy Ox+1 Teos Wafer.

The run sequence for the talc-free Ertalyte® retaining rings is as follows: 1 Teos Wafer+1 Dummy Ox+1 Teos Wafer+2 Dummy Ox+1 Teos Wafer+3 Dummy Ox+1 Teos Wafer+4 Dummy Ox+1 Teos Wafer+5 Dummy Ox+1 Teos Wafer.

A repeat test of 3 Teos wafers was performed for each retaining ring.

Defect Count in Wafers Using Talc-Containing Ertalyte® and Talc-Free Ertalyte® Retaining Rings

Table 2 is a summary of the defect count in wafers for the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings. FIGS. 4 and 5 depict a bar chart of defect results for the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings, respectively. FIG. 6 depicts a bar chart including defect results in wafers for both the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings. “Pre” refers to the defects on the wafer prior to polishing, “Post” refers to the defects on the wafer after polishing, and “Adder” refers to the “Post” defects minus the “Pre” defects.

As shown by the results for the talc-containing Ertalyte® retaining rings, the initial defect count was high, but stabilized at about 200 adders after 4˜5 wafers. The wafer defect count with the talc-free Ertalyte® retaining rings was low initially, and stabilized at about 100 adders after about 3˜4 wafers. Wafers polished with the talc-free Ertalyte® retaining ring had lower defect adders and a quicker break-in time than the talc-containing Ertalyte® retaining ring.

TABLE 2 Wafer Defect Summary for retaining rings made from Quadrant talc- containing Ertalyte ® and talc-free Quadrant Ertalyte ®. Standard Ertalyte - Quadrant Ertalyte - Quadrant(Talc) (No Talc) Wafer # Pre Post Adder Pre Post Adder  1 175 1769 1594 51 401 350  3 20 249 229 35 132 97  6 20 198 178 31 146 115 10 33 239 206 69 185 116 15 45 220 175 65 156 91 21 22 223 201 35 143 108 average 53 483 198 48 194 105 (excludes initial)

The test summarized in Table 1 was repeated with the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings with 3 Teos Wafers with a different slurry than SC-112. The repeat test was performed with a different lot of the brand of slurry SC-112. The results are summarized in Table 3 and FIG. 7. The talc-free Ertalyte® exhibits lower wafer defect adders with the different lot of slurry.

TABLE 3 Wafer Defect Summary of repeat test with different lot of slurry for retaining rings made with talc-containing Quadrant Ertalyte ® and talc-free Quadrant Ertalyte ®. Standard Ertalyte - Quadrant Ertalyte - Quadrant (Talc) (No Talc) Wafer # Pre Post Adder Pre Post Adder 22 113 347 234 115 231 116 23 76 235 159 58 135 77 24 59 256 197 43 118 75 average 83 279 197 72 161 89

To summarize, there is no significant difference in terms of oxide film removal rate and nonuniformity between the talc-containing Ertalyte® and talc-free Ertalyte® retaining rings. For the talc-containing Ertalyte® retaining ring, the wafer defect number stabilizes after 4˜5 wafers with the defect adder of 200. For the talc-free Ertalyte® retaining ring, the wafer defect number stabilizes after just 3˜4 wafers with the defect adder of 100. The talc-free Ertalyte® retaining ring achieves better defect numbers with a faster break-in time on the polished wafers. The repeat test confirms the talc-free Ertalyte® retaining ring has the lower wafer defect numbers.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications can be made without departing from this invention in its broader aspects. Therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention. 

1. A retaining ring for use in a chemical mechanical polishing process, a body of the retaining ring comprises a PET polymer, wherein the PET polymer is free or substantially free of inorganic particles.
 2. The retaining ring of claim 1, wherein the inorganic particles comprise filler particles, nucleating agents, or both.
 3. The retaining ring of claim 1, wherein a portion of the body of the retaining ring comprises the PET polymer.
 4. The retaining ring of claim 1, wherein all or a majority of the body of the retaining ring comprises the PET polymer.
 5. The retaining ring of claim 1, wherein the body of the retaining ring comprises at least one additional polymer blended with the PET polymer.
 6. The retaining ring of claim 1, wherein the body of the retaining ring further comprises organic filler particles dispersed within the PET polymer in an amount less than or equal to 2% by weight.
 7. The retaining ring of claim 6, wherein the organic particles comprise TEFLON particles.
 8. A retaining ring for use in a chemical mechanical polishing process, a body of the retaining ring comprises a polymer, the polymer comprising ethylene terephthalate monomers, wherein the polymer is free or substantially free of inorganic particles.
 9. The retaining ring of claim 8, wherein the inorganic particles comprise filler particles, nucleating agents, or both.
 10. The retaining ring of claim 8, wherein all or a majority of the body of the retaining ring comprises the polymer including the ethylene terephthalate monomer.
 11. The retaining ring of claim 8, wherein a portion of the body of the retaining ring comprises the polymer including the ethylene terephthalate monomers.
 12. The retaining ring of claim 8, wherein the polymer is a copolymer, the copolymer comprising one or more additional monomers.
 13. The retaining ring of claim 12, wherein the additional monomers are selected from the group consisting of phenylene sulfide and etherketone.
 14. The retaining ring of claim 8, wherein a majority of the polymer comprises ethylene terephthalate monomers.
 15. The retaining ring of claim 8, wherein the body of the retaining ring comprises at least one additional polymer blended with the polymer.
 16. The retaining ring of claim 8, wherein the body of the retaining ring further comprises organic filler particles dispersed within the polymer in an amount less than or equal to 2.0 % by weight.
 17. The retaining ring of claim 16, wherein the organic particles comprise TEFLON particles.
 18. A method of polishing a substrate comprising: providing a chemical mechanical polishing apparatus comprising a retaining ring having a body, the body including a polymer including a PET polymer, wherein the polymer is free or substantially free of inorganic particles; retaining the substrate using the retaining ring; and polishing the substrate including the step of placing the body in contact with a polishing pad surface.
 19. The method of claim 18, wherein the body of the retaining ring is free of organic particles.
 20. The method of claim 18, wherein all or a majority of the body of the retaining ring comprises the PET polymer.
 21. The method of claim 18, wherein the body of the retaining ring further comprises organic filler particles dispersed within the PET polymer.
 22. A method of polishing a substrate comprising the step of: providing a chemical mechanical polishing apparatus, the apparatus comprising a retaining ring having a body, the body comprising ethylene terephthalate monomer, wherein the polymer is free or substantially free of inorganic particles; retaining the substrate using the retaining ring; and polishing the substrate including the step of placing the body in contact with a polishing pad surface.
 23. The method of claim 22, wherein the body of the retaining ring is free of organic particles.
 24. The method of claim 22, wherein a majority of the polymer comprises ethylene terephthalate monomers.
 25. The method of claim 22, wherein the polymer is a copolymer, the copolymer comprising one or more additional monomers.
 26. The method of claim 22, wherein the body of the retaining ring further comprises organic filler particles dispersed within the polymer.
 27. A retaining ring for use in a chemical mechanical polishing process, a body of the retaining ring comprises a PET polymer, wherein the PET polymer has organic filler particles dispersed therein and the PET polymer is free or substantially free of inorganic particles.
 28. The retainer ring of claim 27, wherein the PET polymer has less than 0.1% organic particles dispersed therein.
 29. A retaining ring for use in a chemical mechanical polishing process, a body of the retaining ring comprises a polymer, the polymer comprising ethylene terephthalate monomers, wherein the polymer has organic filler particles dispersed therein and the polymer is free or substantially free of inorganic particles.
 30. The retainer ring of claim 29, wherein the polymer has less than 0.1% organic particles dispersed therein. 